1. Field
The presently disclosed subject matter relates to a semiconductor light source apparatus and a lighting unit using the semiconductor light source apparatus, and more particularly to a high power semiconductor light source apparatus including a phosphor layer that can prevent a reduction of brightness caused by thermal quenching and a lighting unit that can also emit various color lights having a large amount of light intensity in order to be able to be used for general lighting, a stage light, a street light, a projector, etc.
2. Description of the Related Art
Semiconductor light source apparatuses that emit various color lights by combining a phosphor layer with a semiconductor light-emitting device such as an LED have been used for business machines, home electronics, etc. Recently, because brightness of the semiconductor light source apparatuses have improved, a range of application for the semiconductor light source apparatuses has expanded to fields such as general lighting, street lighting, a vehicle headlighting, etc.
One method for improving the brightness of the semiconductor light source apparatuses including the phosphor layer, includes providing an excitation intensity of the phosphor layer that is enhanced by flowing a large current in the semiconductor light-emitting device. However, because heat occurs in the phosphor layer due to the large current, the transparent resin can be tarnished. Because the transparent resin is mixed in the phosphor layer, the tarnish of the transparent resin results in absorption of a part of light excited by the phosphor layer, and therefore may cause a reduction of the excitation intensity.
In addition, a reduction of a fluorescent intensity may be caused by a thermal quenching property of the phosphor layer due to the large current. The thermal quenching property is a phenomenon in which a fluorescent intensity of a phosphor becomes reduced when the phosphor is heated at a high temperature. Therefore, because the tarnish of the transparent resin and the reduction of the fluorescent intensity cause a reduction of a light intensity in semiconductor light source apparatuses that include a phosphor layer, it is difficult to improve the brightness of the semiconductor light source apparatuses by simply flowing a large current.
To improve such a problem, a semiconductor light source apparatus using a phosphor layer that includes a phosphor particle without a transparent resin is disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2006-005367). FIG. 1 is a schematic structural view showing a conventional semiconductor light source apparatus including a phosphor layer, which is disclosed in Patent Document No. 1.
The conventional semiconductor light source apparatus includes a semiconductor light-emitting device 95 and a phosphor ceramic layer 92 including a phosphor particle without a transparent resin. The phosphor ceramic layer 92 may not include a transparent resin, and therefore a tarnish of the phosphor ceramic layer 92 may not occur. In addition, because the phosphor ceramic layer 92 is made of a material having a low thermal sensitivity, a thermal quenching may be prevented. Consequently, it may be possible for this semiconductor light source apparatus to improve brightness by simply flowing a large current therethrough.
However, in the conventional semiconductor light source apparatus, after light emitted from the semiconductor light-emitting device 95 is wavelength-converted via the phosphor ceramic layer 92, the light is emitted in the opposite direction of the semiconductor light-emitting device 95. Accordingly, light reflected on the phosphor ceramic layer 92 of the light emitted from the semiconductor light-emitting device 95 may return to the semiconductor light-emitting device 95 and may be absorbed in the semiconductor light-emitting device 95. The reflected light may cause a reduction of light use efficiency.
Moreover, heat generated from the phosphor ceramic layer 92 may be transmitted to the semiconductor light-emitting device 95 and may be radiated from a mounting substrate, on which the semiconductor light-emitting device 95 is mounted. However, because the semiconductor light-emitting device 95 also generates heat, a radiating efficiency of the semiconductor light source apparatus may not be high.
A conventional semiconductor light source apparatus including a phosphor wheel is disclosed in Patent Document No. 2 (U.S. patent application Ser. No. 12/949,776 filed on Nov. 18, 2010). This conventional semiconductor light source apparatus can improve a radiating efficiency of a phosphor layer that is applied on the phosphor wheel by rotating the phosphor wheel. In addition, a transmission type light source apparatus that may enhance the radiating efficiency by locating the phosphor layer on a metallic substrate is disclosed. However, because the phosphor layer includes a phosphor particle in a transparent resin, when a high power light source device is used for the semiconductor light source apparatus for many years, a degradation of the transparent resin may occur.
The above-referenced Patent Documents are listed below and are hereby incorporated with their English abstracts in their entireties.    1. Patent document No. 1: Japanese Patent Application Laid Open JP2006-005367    2. Patent document No. 2: U.S. application Ser. No. 12/949,776 filed on Nov. 18, 2010 and owned by Applicant of the present application.
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include semiconductor light source apparatuses which can emit various color lights having high brightness and can efficiently radiate a heat even when a high power semiconductor light-emitting device is used under a large current as a light source. In this case, light emitted from a high power semiconductor light-emitting device can be efficiently wavelength-converted by a phosphor layer without a reduction of light intensity, because the phosphor layer is located on a radiating substrate and does not include a substantially resin component.
In addition, the phosphor layer can be constructed as a phosphor wheel that can rotate to further improve a radiating efficiency and permanence of the phosphor layer even when the high power semiconductor light-emitting device is used under a large current. In this case, the semiconductor light source apparatus can also adjust a color tone of the illumination light having a large amount of light intensity by connecting a moving module to a motor of the phosphor wheel, and therefore can be employed for various lighting units such as general lighting, a stage light, a street light, a projector, etc.